Deposition of engineered nanomaterials (ENMs) in various environmental compartments is projected to continue rising exponentially. Terrestrial environments are expected to be the largest repository for environmentally released ENMs. Because ENMs are enriched in biosolids during wastewater treatment, agriculturally applied biosolids facilitate ENM exposure of key soil micro-organisms, such as plant growth-promoting rhizobacteria (PGPR). The ecological ramifications of increasing levels of ENM exposure of terrestrial micro-organisms are not clearly understood, but a growing body of research has investigated the toxicity of ENMs to various soil bacteria using a myriad of toxicity end-points and experimental procedures. This review explores what is known regarding ENM toxicity to important soil bacteria, with a focus on ENMs which are expected to accumulate in terrestrial ecosystems at the highest concentrations and pose the greatest potential threat to soil micro-organisms having potential indirect detrimental effects on plant growth. Knowledge gaps in the fundamental understanding of nanotoxicity to bacteria are identified, including the role of physicochemical properties of ENMs in toxicity responses, particularly in agriculturally relevant micro-organisms. Strategies for improving the impact of future research through the implementation of in-depth ENM characterization and use of necessary experimental controls are proposed. The future of nanotoxicological research employing microbial ecoreceptors is also explored, highlighting the need for continued research utilizing bacterial isolates while concurrently expanding efforts to study ENM-bacteria interactions in more complex environmentally relevant media, e.g. soil. Additionally, the particular importance of future work to extensively examine nanotoxicity in the context of bacterial ecosystem function, especially of plant growth-promoting agents, is proposed.

中文翻译：

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工程纳米材料（ENM）对环境相关的有益土壤细菌的纳米毒性-一项重要评论。

预计各种环境隔室中工程纳米材料（ENM）的沉积将继续呈指数增长。预计陆地环境将成为环境发布的ENM的最大存储库。由于在废水处理过程中ENM富含生物固体，因此农业应用的生物固体可促进ENM暴露于关键土壤微生物，例如促进植物生长的根际细菌（PGPR）。陆地微生物对ENM的暴露水平不断提高的生态后果尚未明确了解，但越来越多的研究机构使用多种毒性终点和实验方法研究了ENM对各种土壤细菌的毒性。这篇评论探索了关于ENM对重要土壤细菌的毒性的已知知识，重点关注预计在陆地生态系统中浓度最高的ENM，它们对土壤微生物构成最大的潜在威胁，对植物生长具有潜在的间接有害影响。确定了对细菌纳米毒性的基本理解方面的知识差距，包括ENM的理化性质在毒性反应中的作用，尤其是在农业相关微生物中的作用。提出了通过实施深入的ENM表征和使用必要的实验控制措施来改善未来研究影响的策略。还探索了利用微生物感受器进行纳米毒理学研究的未来，强调需要继续利用细菌分离物进行研究，同时加大力度在更复杂的环境相关介质（例如土壤）中研究ENM-细菌相互作用。另外，提出了在细菌生态系统功能尤其是植物生长促进剂的背景下广泛检查纳米毒性的未来工作的特别重要性。